S. Princely, N. Saleem Basha, J. John Kirubakaran and M. D. Dhanaraju
Beta-galactosidase is one of the important commercial enzymes having several applications in food and pharmaceutical industry. In dairy industry, β-galactosidase has been used to prevent crystallization of lactose, to improve sweetness, to increase the solubility of the milk product. Moreover, it has been used to produce low lactose containing food products for low lactose tolerance people and for the utilization of whey, which would otherwise be an environmental pollutant. Based on its importance, the present research was aimed to isolate and purify β- galactosidase from Streptococcus thermophilus by fermentation process. The enzyme was purified by ammonium sulphate precipitation, dialysis, gel filtration chromatography using Sephadex G-100, and SDS-PAGE and some properties of the purified enzyme like pH, temperature optima and kinetic parameters were determined. Isolate A5 showed highest productivity of 7.76 U/ml with a protein content of 67 μg/mL, pH and temperature optima at pH 7.2 and 40ºC. The apparent Vmax and Km values were found to be 2.8 IU/mL and 3.05 mM, respectively. Specific activity and fold purification of beta-galactosidase was found to be 119.38 & 1.13, respectively. These characteristics of isolated β-galactosidase showed that it could be a promising candidate for various industrial as well as biotechnological applications.
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